The Wakefield committers may hold off-line discussions from time-to-time. Since these meetings are just for the committers and invited wayland experts, summary minutes will be recorded here as time permits
Online Zoom Meeting 9am PDT 30th Mar 2023
Attendees: Maxim Kartashev, Alexey Ushakov, Alexander Zvegintsev, Victor D'yakov, Kevin Rushforth, Olivier Fourdan, Jonas Adahl
xdg-desktop-portal-gnome package was missing in 9.1, but was present in 9.0.
It now comes with 9.1 only with fresh install, system update of an old 9.1 installation didn't work for me, have to install it manually.
While the system now successfully reports version 4 of org.freedesktop.portal.ScreenCast. It is minimum required for restore_token functionality.
xdg-desktop-portal-gnome package comes outdated for both 9.0 and 9.1(latest available 41.2), to be able make screenshot without confirmation for every attempt we need at least 42+ version..
Added handling of negative scenarios when the user partially or completely denies access to screen data.
Now we throw a security exception only if the user denied screen capture at all.
If user is allowed to access only some displays, image data of others will be displayed in black, no exceptions or warnings will be thrown.
If user wants to change previously made decision, newly added Robot.resetRestoreToken() method can be used.
Changed the storage location of restore_token, now instead of a simple file, we use Preferences API.
It's still a file, but now it's a standardized XML file, still storing the token in plaintext.
I don't think this is a problem though.
I also checked probably the most popular product using ScreenCast API - OBS, Open Broadcast Software:
They also use store this token in plaintext in their configuration files.
I also checked how the prototype behaves with Plasma Desktop Session.
When I get the screen data, everything goes without errors, but the data itself is black.
Apparently, it's because I have an Nvidia graphics card.
Another interesting thing is that in response to a call to the Start method, I get a stream that has size, but no position.
This can be a problem, for example when we have two displays with the same resolution.
It is not clear how to distinguish the stream of one screen from the other and thus get the data from the requested display.
We have plans to make it, including introduction of header files, in JDK 21 LTS.
We will know more on our next meeting in 4 weeks from now.
We are usually not making any too risky changes 1-2 weeks before the fork(June 8th), we have only just two months for all this work.
It is not our ultimate goal, but a good opportunity.
We have just begun to continue our work on pure Wayland prototype.
Nikita Gubarkov has some important changes that could be useful for compatibility mode,
he was able to support HiDPI for different monitors using access for underlying wayland subsystem.
He said he will be able to port this changes, and probably, to include them into JDK 21 LTS release.
It is already integrated in our runtime shipped with our products, looks like all the issues resolved so it is time to move to OpenJDK
If this will requires CSR, please do not submit it right before the fork, give it an extra 1-2 weeks.
We could implement some limited support for screenshots for pure wayland.
General idea: as long as we can make at least some tests run just a single window, and don't rely on their absolute position,
but calculate their offsets just from the top left corner of just one window, we can implement robot color picking, and even screenshoting functionality for this window,
by grabbing pixels from associated Wayland buffer.
This will work for some tests, especially performance measuring will be more accurate(e.g. color picking at some points frequently).
Alexander, can we get recent changes for taking screenshots with ScreenCast API, before they reach JDK 21?
pipewire headers requires legal approval before placing them at openjdk github, but I can make a version to use headers files stored in system and share it.
Online Zoom Meeting 9am PDT 2nd Mar 2023
Attendees: Alexey Ushakov, Alexander Zvegintsev, Victor D'yakov, Kevin Rushforth, Phil Race, Olivier Fourdan, Jonas Adahl
Pushed the stable version of screencast code to the sand box
Fix for when focus is outside of xserver window
2 places where window focus transfer does not happen and popup remans open
Tried several 3rd party apps and they behave the same so this OK (is it ? - phil)
Working on build changes to build OpenJDK using screencast on OL 7
Have dynamic loading of functions working. Still relying on the pipewire and spa header files.
On RHEL/OL 8 it does not work when try to run screenshot -outdated pipewire
missing xdg portal support.
So probably can't support such older releases as they will never get all the fixes needed.
Last time when trying to take screenshot on RHEL/OL 9 found does not have xdg portal -
Jonas : said xdg portal gnome backend was there in RHEL 9.0 but lost in 9.1
but this was fixed (9.2) ? Alexander would have to check what version he was using
but this is probably the issue
Alexander: we should talk to jtreg folks about not cleaning out various desktop related
variables from the environment that become more important for wakefield
(DBUS_SESSION_BUS_ADDRESS, XDG_SESSION_TYPE and WAYLAND_DISPLAY)
Phil: agreed but our CI system cleans some of these out too, before jtreg even has a chance.
So multiple things to address.
Jonas : how important is it to support restore tokens in persist mode on RHEL9.x/OL9.x
Phil: This is the support to allow permissions to do screen capture to persist across sessions.
It is very much needed for our automated CI testing systems which reboot after every test task.
Would be hard to support a release where it isn't possible.
RHEL bug about backport restore token portal support: https://bugzilla.redhat.com/show_bug.cgi?id=2174946
On Ubuntu 22.04 have pipewire-0.3 and spa-0.2 - are these API stable ?
Jonas (or was it Olivier?) replied pipewire was api stable as of v 0.3.1.X. So probably fine.
The build work Alexander is doing is important so that we can build on our CI systems
Otherwise a blocker to integrating even xwayland compatibility support into wayland
We build one binary for many distros and versions .. so there's a LCD requirement.
Talked with Nikita Gubarkov who has been working on hidpi on wayland
(see posts on list at https://mail.openjdk.org/pipermail/wakefield-dev/2023-February/000081.html)
Where should he push this ?
(1) Probably into its own branch at https://github.com/openjdk/wakefield
(2) he isn't a project committer so you will need to do it for him
Maxim will hopefully be back soon and will pick up where he left off on wakefield work.
Online Zoom Meeting 9am PDT 2nd Feb 2023
Attendees: Alexey Ushakov, Alexander Zvegintsev, Niels de Graef, Victor D'yakov , Laurent Bourges, Kevin Rushforth, Phil Race, Olivier Fourdan, Jonas Adahl
Updated and slightly redisigned the Known problems and solutions.
The ScreenCast prototype has been redisigned to open/close screencast session during a single call for each screenshot
Some of these changes are already pushed, some will be soon.
It also runs faster than the previous solution.
Did you tried to run some tricky regression tests that require a quick screenshot between some states of controls?
I tried a bunch(they are fine), but haven't run all.
However, some tests that require you to take a screenshot of an icon in the system tray area may fail because an orange"screen is being shared" icon appears while you are taking the screenshot.
Some questions about full support for keyboard/mouse event emulation:
- What is the status of libEI,
- The proposed RemoteDesktop solution doesn't provide a concept for retaining user permission between sessions, such as
restore_tokenin ScreenCast. When can we expect this to be addressed?
- Which solution will become usable for our needs first?
There is active work on libEI, its protocol is being actively developed. At current stage it is already works.
Once it finalized and stabilised the follow up work will be to support it on Mutter, xdg-desktop-portal, xdg-desktop-portal-gnome, libportal and libwayland as well.
libEI is planned to ship with Gnome 45(comes with Fedora 39).
xdg-desktop-portal/issues/850 priority can be bumped. At the earliest it can be shipped with Gnome 44(comes with Fedora 38) if it will be fixed soon.
It should be much easier comparing to libEI.
There is a slowdown on pure Wayland port work. More engineers are expected to join this work. Hopefully Maxim will be back this spring.
X11 compatibility mode, what are the blockers?
We don't have any.
All of them can be worked around by changing the documentation to reflect the current behavior, modified/excluded tests, even some crashes can be avoided by modifying tests.
xorg/xserver/-/issues/1222 posted a possible fix some time ago, but didn't get any traction
All documentation changes should go to the OpenJDK 21 LTS release, even if the work on X11 compatibility mode will not complete by this time. This will allow us to do backports later.
We were able to fix some issues with HiDPI in X11 compatibility mode using some Wayland api besides X11, so probably we will be able to provide our solution.
Online Zoom Meeting 9am PDT 30th June 2022
Attendees: Alexey Ushakov, Olivier Fourdan, Niels de Graef, Jonas Adahl, Kevin Rushforth, Victor Dyakov, Alexander Zvegintsev
Played with gdbus-org.freedesktop.portal.RemoteDesktop API, it looks suitable for mouse/keyboard control for AWT Robot.
Unfortunately it does not support session restoration like gdbus-org.freedesktop.portal.ScreenCast do.
Without it user has to provide "Allow remote interaction" confirmation each time the application is launched..
Is there any plans to add ability to restore session for RemoteDesktop API?
If so, will it come earlier than libEI?
There are such plans, furthermore, RemoteDesktop API will use libEI.
So we can either use RemoteDesktop API or libei directly at some point.
However dates are not clear yet.
A few crashes have been fixed in pure Wayland prototype, and text rendering support has been added.
Software rendering performance is quite good: it is close to 60 FPS( display refresh rate), but it can be worse on a less powerful hardware.
It looks like we can proceed without implementing hardware accelerated pipelines for now.
SwingSet2 works fine, no glitches observed, however input events are not implemented, so there is no way to control the app yet.
We do not expect any several issues with implementing input support.
Online Zoom Meeting 9am PDT 5th May 2022
Attendees: Phil, Kevin, Alexander Zvegintsev, Victor, Zhengyu Gu, Niels de Graef, Maxim Kartashev, Jonas Adahl, Olivier Fourdan, Mario Torres
Alexander : Ubuntu 2204 - no difference from previous releases
Looking at bug where mouse exit event not coming but works fine on native wayland app
Maxim : Nikita has done some work so fonts are being rendered although without hints and AA and sub-pixel but basic rendering working
Also (Maxim) made a preliminary prototype of how we want to start testing pure wayland - custom extension ..
He wasn't able to merge into openjdk repo [Kevin : Maxim missed a step in his project acceptances]
Code available through JB runtime repo
Maxim gave a quick demo of test framework
Lanuch a custom weston instance with Maxim's plugin so you aren't updating the running
desktop so no admin permissions required
The plugin gives access to weston internals -
provides wayland protocols which could be implemented for some other server
location of surface in abs coords
set location ..
grab portion of screen
get pixel color
would like someone to code review - Java side OK but plugin code is less obvious
Why doesn't work it with weston 10 when it works with weston 9 .. once you get
into accessing internals you really need to build against the exact version of weston you are targetting.
This testing effort is intended to be a stop-gap until we have a proper solution to running tests on
the wayland desktop - not imagined as a solution we can deliver as part of OpenJDK
Online Zoom Meeting 9am PDT 7th April 2022
Attendees: Alexey Ushakov, Olivier Fourdan, Niels de Graef, Jonas Adhal, Sergey Bylokohov,
Alexander Zvegintsev, Zhengyu Gu, Phil Race, Kevin Rushforth, Victor Dyakov
Working on pure wayland, can show AWT and Swing frames with sime simple rendering in paintComponent
Nikita working on font rendering. Will push to branch on openJDK when ready.
3rd thing is AWT robot - Maxim is providing custom extension to Weston instance to get it working.
Alexander : does extension cover screen shot + key press : yes - works even for multimon ...
this is useful for testing but not for production
Sergey : how difficult to install this extension ?
Alexander: Reported a bug about XOR rendering but it could be a driver bug ?
Screencast still not usable because have to configure it manually every time you start a session
So weston extension looks more promising (for testing)
Need some scripting support
Jonas: maybe not running in a sandbox or something - should be possible to make it remember
what you selected in a dialog.
Maybe be missing a way for portal to associate request with application ID
Screencasting portal configures a token that should make it possible
Screenshot portal doesn't remember that _yet_ though
You can follow this issue for the latter: https://github.com/flatpak/xdg-desktop-portal/issues/649
Niels De Graef : Note that a wl extension protocol that disables security features like that probably won't fly in any compositor
( Jonas & Niels?) : AI: Are there any particualr JDK requirements around input methods - there is a slow moving project
to update in update flawed gtk3 4 protocol .. Phil will have to get back on that after asking around.
Online Zoom Meeting 9am PST 10th Mar 2022
Attendees : Maxim, Olivier Jonas, Alexey, Niels De Graef, Phil, Alexander, Kevin, Victor
Alexander : has been doing testing of current JDK on Oracle Linux 8.5
This uses gnome 3.32 - old gnome shell - so not getting recent fixes
So just a point of reference
Getting some new failures (tests that passed before ) on Ubuntu 21.04 and 21.10 - likely this is due to updated OpenGL drivers
Some JDK screen shot tests failing but need to implement something so not an unexpected problem
Olivier : update on Drag and Drop - the upstream fixes have landed in gnome 42 and 40
X.org not likely to be removed any time soon by any distro as most are oonly just switching to
wayland as the default. So we have time. Perhaps some cutting edge distro will be first but not soon.
Alexey : Up date on pure wayland work - trying to support just one AWT button but needed to bring in
whole AWT hierarchy - meaning a lot of the equivalent of the Xawt toolkit.
Kind of working but faced with problem of placing location of windows on desktop
can only provide coords for popup surfaces We've talked before about this being part of the design philosophy of wayland
Surely this is needed even for applications that try to place their windows relative to each other ?
Jonas: this has come up in discussions about whether it makes sense ..
GIMP might need this ? Well maybe not GIMP because it is moving away from multiple images but
some medical applications have a need .. but it may be more like session management
1st time launch rearrange your windows. then the extension protocol can be used to save this.
[ Editor : I'm not sure if this would work for JDK needs and how would we expose that protocol to apps ?
It can't just be "java" as that's the platform not the application.]
Alexey is focused on the rendering side. Dmitry Batrak will be looking at event handling.
And Maxim is thinking about Robot - prototyping some new approach to automated testing ... run tests in a weston instance on top of X11 ?
Only useful for testing. Using a custom protocol extension.
Peter Hutterer working on libei and has made a 0.2 release Jonas working on it too.
Concentrating on 2 parts : capturing events and other is sending input events
feature where input captured from compositor - like Synergy which forked into Barrier and then again
That project is to share input devices across multiple computers mouse events go to the other computer when the mouse
goes off edge of screen and emulate events on other computer
API mostly written down but not yet stable.
Peter Hutterer made a 0.2 pre-release.
Blog here :
In the world of sandboxing and flatpak not guaranteed that they have same version of a library.
So not going to make it into any distro even as a pre-release until API and wire format are stable.
Online Zoom Meeting 9am PST 10th Feb 2022
Attendees: Kevin, Victor, Olivier, Mario, Aleksandr, Alexey Ushakov, Maxim Kartashev, Sergey, Zdenek, Zhengyu, Dalibor
We went through all of the open issues on the WIki. Aleksandr will update the bugs with the latest status. The suggestion was made to group them by their status into 2 or three groups (unresolved, fix in progress, resolved). For the unresolved issues, they could be prioritized.
1. JDK-8280982 : java.awt.Robot taking screenshots
Needs to be solved by the Portal team. Not limited to Wayland. This is the number one issue in terms of importance. There is a bug filed against Portal in the flatpak project.
We spent some time discussing the current limitations. What we ultimately need is something that only needs to be configured once by an administrator, and will not produce a popup. Another limitation that needs to be overcome is that the current workarounds only capture the entire screen, which is not sufficient for an API that is often used to read small regions (or a single pixel). This will be too slow. Another idea was discussed to throw a security exception in the screen capture API, but that would require a spec change. It's also not what Java2D does on other platforms (e.g., Mac) when the proper permissions haven't been granted.
2. JDK-8280983 : java.awt.Robot emulating keyboard/mouse events
No new information. Solving this using libEI will be best, and will also solve one of the below issues, but there is no time frame as to when we might expect a fix.
Additionally, using libEI should fix following:
JDK-8280995 : X11 compatibility: Robot.mouseMove does not visually move mouse cursor
JDK-8280990 : X11 compatibility: XTest emulated mouse click does not bring window to front.
JDK-8280988 : X11 compatibility: Click on title to request focus test failures
The last of the above two can be worked around by test changes, but using libEI is a better solution.
3. JDK-8280993 X11 compatibility: Popup menu dismiss in X11 compatibility mode.
This one should be fixable.
4. JDK-8280991 X11 compatibility: fake configure event for XRandR emulation
Should already be fixed in latest version
5. JDK-8280985 X11 compatibility: Wayland crash on huge window
6. JDK-8280987 X11 compatibility: crash when mapping a lot of windows
There are two issues here: one is that we are running out of file descriptors, the other is that this will fill up the Wayland buffers. The first is a simple fix (In progress). The second fix in Wayland itself, not XWayland. It's also in progress, but is a complex fix.
7. JDK-8280992 X11 compatibility: Custom colored cursor might be displayed in black and white
Aleksandr will file a bug if he can come up with a simple reproducer
There are additional issues specific to pure Wayland mode that still need to be filed (this needs more discussion).
Online Zoom Meeting 9am PST 27th Jan 2022
Attendees : Olivier, Phil, Kevin, Aleksandr,, Victor, Niels De Graaf, Alexey Ushakov, Jonas, Sergey, Zdenek, Zhengyu
Ubuntu 20.04 - some test problems - tests passed on 20.10 and 21.04
Memory leak tests - need to increase xMax heap
Mouse enter/exit events
Not always clear if Java problem or Wayland
Let's not spend/waste time on older OSes even LTS versions they'll never have
all the support we need anyway.
Working on migrating bugs / issues just documented on internal wiki to JBS using release==internal
Olivier : DnD also fixed in new OSes
Xwayland is not involved in DnD or copy/paste - standard x atoms
Wayland compositor or applications - x app knows nothing about wayland native so it
is the wayland compositor which does the translation
So doing DnD mutter has to map X11 window and use that to translate
Upstream Gnome 42 fix not yet backported to gnome 41 used by Fedora 35 ..
Can you use latest mutter from main on older OS ? Olivier or Jonas (?) - possible but sounded like a bunch of steps
he will find docs on this
Ed : I think this is the doc meant : https://gitlab.gnome.org/exalm/jhbuild-steps/-/wikis/JHBuild-on-Fedora
Alexey : trying native wayland port rendering using J2D s/w rendering.
Need to fit wayland model to our surface architecture ? Will create a branch in project repo.
Also (AI) will update wiki with info on this
Niels : updated wiki to more clearly describe JDK issues where there are gaps in wayland support
Do AWT Robot docs offer a "way out".
Note that some platforms require special privileges or extensions to access low-level input control. If the current platform configuration does not allow input control, an
AWTExceptionwill be thrown when trying to construct Robot objects. For example, X-Window systems will throw the exception if the XTEST 2.2 standard extension is not supported (or not enabled) by the X server.
Applications that use Robot for purposes other than self-testing should handle these error conditions gracefully.
These words are not intended to say you can be conformant - more about advice that you
may need to update settings add packages to mke your desktop supported.
Analogies such as makung sure you have required X11 packages installed and headful support is available.
Zdenek : Fedora rawhide - dev version of Fedora may be a way of getting VERY latest ahead of a Fedora release
Online Zoom Meeting 9am PST 13th Jan 2022
Attendees : Olivier, Phil, Kevin, Aleksandr, Dalibor, Victor, Niels De Graaf, Alexey Ushakov, Jonas, Mario
he topic of the day was a discussion around Alexey's email to the mailing list ..
proposing what we might do for the "full" wayland native port and the various points it raised
Note: Alexey will add a fleshed out version on the project wiki.
The proposal suggests we'd code to the low level wayland APIs rather than using a high level toolkit (ie GTK4)
As previously observed we should explore both. Probably we could get bootstrapped a lot faster with GTK4
and it would give flexibility for backends so we'd probably not need to create an OGL and Vulkan backend ..
if Vulkan was an option on that distro then we'd expect the underlying Cairo (?) based renderer to be
using it or have it as an option.
Likely there are pros and cons to both options. GTK4 might make assumptions or so things in a way
that isn't compatible with some other functionality. A low-level port might mean a lot of re-inventing
the wheel and having to use functionality that is distor-specific but would have been hidden / abstracted
by the platform GTK 4.
So due diligence on both options, and not expecting completely smooth sailing for either.
Ease of implementation and maintenance and portability are strong arguments, but so are flexibility and
internal consistency in behaviour and behavioural compatibility with the existing X11 implementation.
So if doing it "right" is more work, we'll have to absorb that, and we want a stable base so we aren't
in a perpetual maintenance game.
Mario observed that we need to not get ahead of ourselves because we still have the list
of technical challenges that need to be resolved that apply to X compat mode and to a native port too.
We'll work on those but whilst they work through the eco-system over 2 years (?) we could be
doing something useful ..
One element of the proposal not directly related to wayland is we could merge EDT and Toolkit thread
since we no longer need these separate for applets. Possibly, but we kick off a new thread for modal
dialogs too .. could this be special cased ? Might depend on whether you can limit what happens
in such a case but I'm not sure you can.
We do have these documented on the wiki but it needs another pass to have a consitent format
- what the problem is
- what JDK can do
- what we need from the wayland ecosystem
- how much of a blocker it is
- can we "tweak" the spec - at the cost of making backports harder
We should look at this soon so we can get started on spec tweaks we think may be unavoidable but acceptable ..
Eg What's acceptable for screenshots ? We can't deprecate but can we make something optional ?
Alex Z: Is the SplashScreen API supportable ?
Apparently splash screens display in top lefe (the window positioning problem)
A splash screen (output only) surface role could probably be proposed upstream.
it'd just need a fallback implementation for compositors that doesn't support it, e.g. a dialog
Maybe similar to this PiP request : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/132
For more info on roles: https://wayland-book.com/surfaces/roles.html
Add input to this existing issue : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/67
Is there a library ? Like ATK ?
There are existing DBUS based A11Y APIs ..
For the accessibility protocol Jonas is talking about: https://www.freedesktop.org/wiki/Accessibility/AT-SPI2/
For a quick overview of what Emmanuele did for accessibility in GTK4: https://blog.gtk.org/2020/10/21/accessibility-in-gtk-4/
Online Zoom Meeting 9am PST 16th Dec 2021
Attendees : Olivier, Phil, Sergey B., Kevin, Aleksandr, Dalibor, Victor, Niels De Graaf, Alexey Ushakov
Previously discussed upstream DnD bug is fixed upstream - maybe backported to gnome 41 branch ?
On Ubuntu 21.04 using JDK in Xwayland compat. mode DnD from one java app to another (eg) JEdit
gets dropped on native terminal window instead.
DnD is handled by the wayland compositor acting as proxy - Olivier has seen similar issues if you
have wayland native under X11 then it hits the window underneath this should be fixed if you try
Fedora 35 - Ubuntu 21.04 slightly older and presumably doesn't have this fix.
Sergey asked Alexsandr if his DnD testing was using the Robot API or by hand and whether
it is even theoretically possible if wayland doesn't report global screen coords for a window so you
can't move the mouse to a screen position of another windows.
i.e can't move mouse from window 1 -> windows 2 because don't know where window 2 is ...
In other words we have wiggle room in the APIs - and code in the implementation - such that SetBounds calls for a top-level
might be ignored or adjusted, but we rely on correct answers from GetBounds
Olivier : this should actually be OK because in compat mode the apps are talking to an X.org server albeit one acting as a bridge (ie Xwayland)
Some similar discussion where you just want to move the focus from Button A in WIndow 1, to Button B in Window 2
and you need to know the position
In wayland you could set the position by saying loc (x1,y1) in WIndow 2 even if you don't know the real position of Window 2
Not clear (to me) what this would look like for DnD as you want to move the mouse and see it cross the screen outside window boundaries ..
(some of the above needs verifying - outcome of the discussion was not 100% clear to me)
Screencast API is used for automated testing by wayland devs
Would we need to provide new APIs ? And respecify so that existing APIs are "optional".
Could get confusing because other platforms will not have the same issue or model.
Assumes that xwayland compat mode would not need this respecifying to give us backport options.
All too early to know.
Noted that GTK4 was re-specified in a similar way so that things that don't work on wayland are no longer part of the API
How is multi-mon handled in this scenario where you can't position/get position ? Full screen too ?
Full screen is a special case, and you may be able to specify the monitor for a window but that's about it.
Sergey : How does it work for custom decoration on pure wayland
Olivier: Some history here expected client-side decorations was always the answer - so custom decorations would naturally fall from that.
But KDE folks not happy - wanted server side decorations for consistency on the desktop so there is an optional protocol for a wayland
compositor but the client needs to be able to fall back to client-side in case that protocol is not supported on a compositor.
Is there a deadline to ship xwayland compat JDK ?
None yet - still working through these issues - a deadline might be when (say) RHEL shipped without x.org .. which would be a real problem if
we didn't have all the answers ready.
Online Zoom Meeting 9am PST 2nd Dec 2021
Some progress on issues previously seen - some upstream bugs filed and/or fixed.
As reported on the mailing list the DnD issue previously discussed has been fixed upstream
Mapping a single large window : 2 bugs : 1 in wayland 1 in xwayland
Problems with creating a large number of windows is because wayland has fixed buffer sizes for the number of mapped windows
Four, 4K buffers for file descriptors, other requests .. they can fill up
Variable buffer sizes is tricky and a proposed patch is under discussion but not yet accepted.
Some of these problems do not affect running native directly on the hardware with Glimmer and DRM available
but only affect running in a VM where shared memory is used instead.
Online Zoom Meeting 9am PST 18th Nov 2021
We went through some of the issues raised by individuals on the call
Wayland does not provide access to the absolute coordinates of a window on a desktop
or allow specifying it. Whereas X window managers don't make guarantees about positioning but
generally do honour a request and do allow querying. We may have some work to do in making
things work as well as possible with the different approach of wayland
There's (some) discussion here : https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/72
There was discussion of ideas such as creating an invisible window that spanned the entire screen
and creating other windows as children of that but this may be fighting another battle where child
windows are assumed to be transient windows.
Focus issues .. and bringing a window to the front or sending it to the back ?
Maybe a way to bring a window to the front with focus but not sending to the back
XDG activation protocol can ask for attention and that usually means being raised to front
Drag and Drop bugs - Alexander having some trouble on Fedora 35
Solutions to some of the challenges are still evolving and different distros may provide different solutions.
There was a discussion and agreement about the importance of implementing to a level that abstracts away
platform-specific code. Coding to something that depends on a particular library that a platform
may not choose to deliver makes our task harder and nearly impossible to deliver one OpenJDK binary
that could run on multiple distros.
All (or at least most) of this is still applicable to both the xwayland case and the wayland case.
Focus for now continues to be on the former. Too early to say if GTK4 or lower-level approach will
ultimately win out for OpenJDK needs.
It was observed that GTK and its print dialog drive you to xprint, which may not be what we want.
Not yet looked into what printing will look like in a native wayland port.
Online Zoom Meeting 9am PDT 16th Sept 2021
Attending : Wakefield committers from Oracle, Redhat, JetBrains and Amazon as well as Wayland developers from Redhat who were invited by Mario.
The intent of this meeting was to have a productive dialog between the OpenJDK developers and Wayland community developers to come to a better shared understanding of the technical challenges and current state of Wayland and identify avenues of investigation.
Some opening remarks were about the Wakefield infrastructure, including this wiki, the Wakefield mailing list and the Wakefield repo.
Now they are up and running we expect to use the mailing list for most communications and document progress etc on this wiki page.
Branches should be created in the Wakefield repo for all work / experiments etc. Don't use the master branch.
In other words, we should use the project infrastructure for everything and publish contributions and ideas there.
The major topic of conversation was around the options for JDK for capturing screenshots and synthesising input events - both for running in X11 compatibility mode or as a native Wayland client
Screen capture is done today by calling a GTK API which is no longer exposed in GTK 4 because core wayland doesn't support it.
We need an alternative, (JDK has a pure X11 fall back based on xwd but we didn't touch on that - it has the same issue)
A few things were thrown out that might merit investigation
The libportal abstraction / helper layer is probably what we'd want.
It is unclear (to me the note taker) if this is readily available on distros alongside wayland - we can't ship it ourselves and it ilikely needs more than a client-side library anyway
JDK for X11 today needs the functionality of the XTEST X11 extension protocol to support the input event side of things.
The wayland desktop answer for this is probably going to be https://gitlab.freedesktop.org/libinput/libei but it is still in development.
It is very unlikely that distros will be ready to ship all the pieces we need in the next 12 months. So the "short term" goal may actually need to wait for somewhat longer than that.
What is the API the clients used for rendering to the wayland client off-screen surface ? GTK defaults to OpenGL (EGL) and falls back to shared memory (ie some software rendering and a copy)
There is also an experimental Vulkan backend.
We use Xrender as the default Linux rendering pipeline today. Maybe we could use OpenGL for the X.org desktop too ? Yes, it is possible that we end up making improvements to the XGL pipeline as a consqeunece of adding EGL support for Wayland so that we could make OpenGL the default there (X.org) too. But it would be a side-benefit not the main goal.
What are people using for window decoration since the wayland model is that the client does the decoration ?I didn't catch all the options here seems there are a few
There was also a question about hidpi causing fuzziness of X11 apps especially for fractional scaling.
The wayland devs confirmed it is a known issue but difficult to solve without making X11 apps far too small to be legible.
The wayland devs input seems to be essential to us navigating a very complex and evolving landscape.
We agreed we need to go off and study some of these APIs and come back with follow up questions when ready.